A Beginner’s Guide to Coffee

On average, a coffee tree produces about 2.2-4.4 kg (1-2 pounds) of roasted coffee beans annually. Kicking Horse Coffee presents the numbers in a more relatable way: a 2-cup-a-day coffee drinker consumes the annual harvest of 18 coffee trees.

Each coffee cherry contains only two beans. (The anomalies that contain only one bean are called “peaberries.”) According to Kicking Horse, it takes 2,000 cherries (11 kg/5 lbs) to make 2.2 kg (1 lb) of roasted coffee, and a “good” picker can between 220-880 kg (100 and 400 lbs) per day.  After picking, beans must be sorted by hand or, if a grower’s budget allows, a flotation tank. (Ripe beans sink to the bottom making for faster sorting.)

The bottom line? Coffee harvesting is exacting and difficult work. (Labour is a big part of production costs. More on that in the Fair Trade section.)

Extracting the Bean

Coffee cherries consist of several layers: outer skin, mucilage, parchment skin, silver skin and, finally, the two beans. Getting to the beans is not exactly easy. Once the fruit is removed, the beans must be dried to a moisture content of about 11-12%. There are two main types of processing involved in removing the fruit from the bean: wet and dry.  

• Wet or Washed: The beans are soaked in water so the pulp of the cherry will ferment and fall away. The pulp-free beans are then washed and laid in the sun or placed in a kiln to dry, before the final step of machine husking. The end result is cleaner, more acidic, and lighter-bodied coffee.   
• Dry or Natural: Cherries are laid out in the sun for about two to three weeks until the fruit shrivels up. The dried husks are then removed mechanically. The coffee must be turned regularly to ensure it does not rot. The coffee that emerges from these beans tend to be heavier-bodied and sweeter, with fruity flavours.
• Semi-washed: In this mechanized process, water is used to wash away the skin and pulp. The beans are then dried in the sun or in kilns. Semi-washed coffees have lower acidity and more body, with some intense flavours. Indonesian semi-washed coffees, in particular, may have woody, earthy, or spicy flavours.

The green beans that emerge from this process are then shipped to roasters for completion.

Roasting

When coffee beans leave the farm, they don’t have the rich, brown colour we all know and love. They are green, as shown here. Green coffee beans have virtually no aroma and a bitter taste.

Roasting transforms the green beans, infusing them with their highly recognizable aroma and various flavours. Generally, lighter roasts preserve the acidity along with the herb and fruit notes, while darker roasts have more smoky flavours and lower acidity.  (Coffee & Health) Roasting also changes the colour of the beans and brings out some of the natural oils.

You can parse the list of roasts in many ways--Coffee Cuppers has nine categories on its site--but the basic divisions are light, medium, and dark. Each roast has typical characteristics:

• Light: A tan or cinnamon colour, fruity taste, and low acidity. These beans are dry, compared to darker roasts, which have visible oil. Light roasts work well for mild, creamy coffees because of their subtle flavour.
• Medium: Light brown and balanced between sweetness and acidity. Well-suited for a cup of strong, black coffee. Medium-dark roasts tend toward a more bittersweet flavour.
• Dark: Almost black in colour with an oily appearance and strong, bitter flavour. Dark roasts are good for lattes. Among the darkest of the dark are French, Italian, and Spanish roasts, which have a burnt flavour and aroma.

My recent purchases show the differences in roasts. The Guatemalan beans on the left have a light colour and virtually no oil, while the Indonesian beans on the right are significantly darker and oilier.

As with any food that is cooked, the roasting process causes a number of chemical reactions in coffee beans. There are five main stages, outlined in The World Atlas of Coffee:

• Drying: Coffee beans cannot turn brown if there is water present (nor can any food). In the first stage of roasting, water evaporates from the beans. There is virtually no aroma and no colour change at this stage.
• Yellowing: With the water gone, the beans begin to change colour and start emitting an aroma that smells like basmati rice or freshly baked bread.
• First Crack: As the roasting process continues, gases and water vapour build up inside the bean, causing it to pop and crack. At this point the coffee flavour starts to develop.
• Roast Development: The length of this stage will determine the final flavour and aroma of the coffee beans. The longer the roast continues, the lower the acid and the higher the level of bitterness.
• Second Crack: The second crack is not as dramatic as the first, but it is here that the oils in a bean start to surface. Going beyond the second crack is risky since the beans can catch fire. Coffees that reach this stage tend to have a heavily roasted or burned taste, like French or Italian roasts.

After roasting, the beans are quenched, or cooled, to ensure the roasting process is abruptly stopped. Without this step, the heat within the beans could continue to “cook” them, potentially changing the flavour and aroma and imbuing the coffee with an off-taste.

The roasting process can result in the creation of over 800 volatile aromatic compounds--more than are found in wine. Each cup of coffee will have only a small number of these compounds, but they still pack a punch. As James Hoffman notes, “...the smell of freshly roasted coffee is so complex that all attempts to manufacture a realistic, synthetic version of this smell have failed.”

Further Viewing. For an interesting view of the roasting process, watch Roasted, a short video that places a camera inside a coffee roaster. (FYI: The video also promotes GoPro cameras.)